Conventional systems for automatically opening and closing a sliding door in a vehicle include a power drive assembly for moving the door so that the door can be moved between a fully closed position and a fully open position. Examples of such systems are described in WO 97/44559; and U.S. Pat. Nos. 6,481,783; 6,464,287; 5,644,869; 5,536,061; 5,434,487; 5,203,112; and 5,168,666.
In several of the examples of power sliding doors of the prior art, the drive assembly remains engaged even when the power is not activated. Thus when an operator wishes to manually open or close the door, the operator must overcome the drag produced by the drive assembly. In moving the door with the drive assembly engaged, the motor must be rotated in addition to all of the gears or other hardware of the drive assembly. This can make manually opening and/or closing of the door difficult to achieve due to the increased force required to move and/or rotate the drive components.
Additional problems exist with prior art door openers. For example, many door opening mechanisms include a gear rack which the drive acts against. While such systems work well, they can suffer from disadvantages in that the rack is typically visible to individuals outside the vehicle and can be unsightly and the rack must be provided with a lubricant that can attract and retain dirt and other contaminates which can adversely affect operation of the opening mechanism over time.
U.S. Pat. Nos. 6,481,783 and 6,464,287 show an opening system which employs a form of chain drive rather than a rack. U.S. Pat. No. 5,168,666 shows an opening system which employs an endless belt having a portion to which the door is attached. Other systems employ a cable which is attached to the door and moved my the drive mechanism.
All of these prior art systems suffer from disadvantages and/or problems including, the weight of the mechanisms, their complexity, a resultant poor aesthetic appearance and/or the reliability of the mechanism over time.